Compositions for inhibiting corrosion and ash deposition in fossil fuel burning equipment

ABSTRACT

MARKED INHIBITON OF CORROSION AND ASH DEPOSITION IN FOSSIL FUEL BURNING EQUIPMENT IS ACHIEVED BY UTILIZING IN THE OPERATION OF SUCH EQUIPMENT ADDITIVE COMPONENTS COMPRISING SOURCES OF SILICON AND MAGNESIUM, THE PROPORTIONS BEING SUCH AS TO PROVIDE A COMBINED SIO2 AND MGO EQUIVALENT WHEREIN THE SIO2:MGO RATIO IS GREATER THAN 2:1. THE ADDITIVE COMPONENTS CAN BE ORGANIC COMPOUNDS, INORGANIC COMPOUNDS OR MIXTURES THEREOF, AND SUCH COMPOUNDS OR MIXTURES THEREOF CAN BE EITHER SOLUBLE OR DISPERSIBLE IN WATER OR OIL. THEY CAN BE INDIVIDUALLY OR COLLECTIVELY BLENDED WITH BULK FOSSIL FUEL PRIOR TO BURNING, INTRODUCED TO THE COMBUSTION ZONE SEPARATELY FROM THE FUEL, OR IN THE CASE OF FURNACES AND BOILERS, INTRODUCED DIRECTLY TO THE ASH DEPOSITION ZONE. IN THE COMBUSTION OF FOSSIL FUELS IN FURNACES, BOILERS AND DIESELS, THE ADDITIVE COMPONENTS SHOULD BE PRESENT IN AMOUNTS TO PROVIDE AT LEAST 0.05 PARTS BY WEIGHT OF COMBINED SIO2 AND MGO EQUIVALENT TO EACH PART BY WEIGHT OF ASH IN SAID FUEL. IN THE COMBUSTION OF FOSSIL FUELS IN GAS TURBINES, WHEREIN EITHER OR BOTH VANADIUM AND ALKALI METAL WILL BE PRESENT IN THE COMBUSTION PRODUCTS, THE ADDITIVE COMPONENTS SHOULD BE PRESENT IN AAMOUNTS TO PROVIDE AT LEAST 2 PARTS BY WEIGHT OF MAGNESIUM TO EACH PART BY WEIGHT OF VANADIUM IN SAID FUEL, WITH THE SIO2: MGO RATIO OF SAID COMPONENTS BEING SUCH AS TO PROVIDE AT LEAST 2 PARTS BY WEIGHT OF SILICON TO EACH PART BY WEIGHT OF ALKALI METAL IN SAID FUEL AND IN THE AIR COMBINING THEREWITH ON COMBUSTION.

70 0 L/A/TREATEU 45H Comma/01v kn June 18, 1974 J SCQTT 3,817,722

COMPOSITIONS AND METHODS FOR INHIBITING CORROSION AND ASH DEPOSITION IN FOSSIL FUEL BURNING EQUIPMENT Filed Aug. 17, 1972 Si/Na RATIO United States Patent @fice 3,817,722 Patented June 18, 1974 Int. Cl. C101 1/28 US. CI. 4476 7 Claims ABSTRACT OF THE DISCLOSURE Marked inhibition of corrosion and ash deposition in fossil fuel burning equipment is achieved by utilizing in the operation of such equipment additive components comprising sources of silicon and magnesium, the proportions being such as to provide a combined Si and MgO equivalent wherein the SiO :MgO ratio is greater than 2:1.

The additive components can be organic compounds, inorganic compounds or mixtures thereof, and such compounds or mixtures thereof can be either soluble or dispersible in water or oil. They can be individually or collectively blended with bulk fossil fuel prior to burning, introduced to the combustion zone separately from the fuel, or in the case of furnaces and boilers, introduced directly to the ash deposition zone.

In the combustion of fossil fuels in furnaces, boilers and diesels, the additive components should be present in amounts to provide at least 0.05 parts by weight of combined SiO and MgO equivalent to each part by weight of ash in said fuel.

In the combustion of fossil fuels in gas turbines, wherein either or both vanadium and alkali metal will be present in the combustion products, the additive components should be present in amounts to provide at least 2 parts by Weight of magnesium to each part by weight of vanadium in said fuel, with the SiO' :Mg0 ratio of said components being such as to provide at least 2 parts by weight of silicon to each part by weight of alkali metal in said fuel and in the air combining therewith on combustion.

This invention relates to compositions and methods for inhibiting corrosion and ash deposition in fossil fuel burning equipment wherein additive components comprising sources of silicon and magnesium are employed in proportions such as to provide a combined SiO and MgO equivalent, wherein the SiO :MgO ratio is greater than 2:1, and preferably in excess of 3:1. Increasing the SiO :MgO ratio provides added benefits in the inhibiting of corrosion and ash deposition and the extent of increase of this ratio is limited only by economic factors. In the operation of gas turbines, for example, it is desirable and economically practical to employ a SiO :MgO ratio of 6:1 and higher with high sodium fuels.

BACKGROUND OF THE INVENTION The use of poorer quality ash containing fuel oils can be a significant factor in reducing operating costs of fossil fuel burning apparatus, and because fuel represents a major item of expense, the ability to burn low cost fuels will, in many cases, be the determining factor in the type of equipment selected for power generation or propulsion systems. (We are not here concerned with gasoline operated vehicular engines.) It is desirable in many instances from an economic standpoint, therefore, that furnaces, boilers, diesel engines and gas turbines, operate on low cost liquid fuels including heavy distillates, diesel oil, crude oils, and residual-type fuel oils.

The problems associated with the use of fuels containing inorganic ash contaminants are well known, although the mechanisms which result in high temperature corrosion and ash deposits in fuel burning apparatus are complex and little understood. It is obvious that certain types of fuel burning apparatus can operate more efliciently and with less problems with such ash contaminated fuels than others, and thus have an inherent advantage both in terms of fuel and maintenance costs. Heating and power generating boilers and furnaces are capable of burning relatively poorer grades of fuel than internal combustion engines, with the diesel engine having a definite superiority in this respect as compared to the gas turbine. Although the basic problem of burning ash containing fuels is that of corrosion and ash deposits, it is obvious that equipment design and operating conditions differ significantly for these three categories of fuel burning apparatus, and that the fuel requirements and economies are significantly different.

It is well known that the nature and quantity of ash contained in liquid hydrocarbon fuels varies with the source of the crude petroleum oils, and that such variation carries over to residual oils which are derived from these crudes in refinery processing. The ash of such oils generally has low melting temperature in the range of 950 F.1200 F., and contain, inter alia, vanadium, alkali metals and sulfur compounds which are generally considered to be the primary causes of corrosion and of ash deposits on metal surfaces exposed to the elevated temperatures of the combustion products leaving the combustion zone. Although these components are generally considered to be the causative factors which are of primary significance in high temperature corrosion and ash deposits, it is believed that other non-combustible inorganic compounds that may be present in fossil fuels also play a lesser role, or may even, at times contribute to a significant degree to either the corrosion problem, the ash deposit problem, or both. For example, gas turbine corrosion and deposits have been problems in blast furnace gas operations where vanadium was not present.

The use of magnesium, silica and, to a certain extent, combinations thereof, to minimize corrosion and ash deposition in fossil fuel burning equipment has long been known in the art. By way of illustration, US. Pat. No. 3,003,857, issued Oct. 10, 1961 to William H. Carls, Jr. shows the effectiveness of additives providing a source of silica in controlling ash deposition when operating gas turbines with low grade oils. US. Pat. No. 3,316,070, issued Apr. 25, 1967 to James F. Scott shows the effectiveness of additives providing a source of silica at fuel combustion temperatures on the improvement of combustion of diesel oil, residual fuel oil and mixtures thereof and in preventing of the fouling of ports and valves by deposits in the operation of diesel engines.

Various patents can be cited disclosing the use of sources of magnesium, aluminum, zinc, calcium and other metal compounds in a form to provide the metal oxide at combustion temperatures as a means for combatting the corrosion and ash deposition problem due to the vanadium content of various fuels. A number of patents, including US. Pat. No. 2,781,005 and British Pat. Nos. 761,360 and 800,445, disclose the introduction of magnesium in the form of naturally occurring clays, talc, and the like which would provide a combined source of MgO and SiO,, at fuel combustion temperature. In such natural products, the ratio of silica to magnesia is generally in the 1:1 to 2:1 range.

While these various type additives have shown considerable effectiveness in gas turbines and other combustion systems, such as boilers and engines where metal surfaces exposed to combustion products may be in the 800 F.-1300 F. range, there has been considerable emphasis in recent years to achieve better efiiciency and higher engine output by increasing equipment operating temperatures. However, new problems emerge concerning both ash deposit and corrosion as metal temperatures are increased significantly above the melting point of fuel oil ashes and in particular in the case of gas turbines exceed 1400 F., and thus far additives effective at the lower temperature range have proved quite ineffective in controlling both corrosion and deposits at higher operating temperatures.

The problem of corrosion of metals exposed to combustion gases from the burning of ash containing fuels at temperatures below about 1300 F. is subordinate to the problem of oil ash deposits which adhere to furnace tubes, exhaust valves, turbine blades, etc., which have the effect of reducing rated power output eventually to a point necessitating shutdown and cleaning of the equipment. While corrosion may also be an attendant problem in some cases, depending upon the type of combustion equipment, temperature level and fuel quality, it does not usually jeopardize the intended equipment life.

The use of silicon additives has demonstrated effectiveness in modifying the nature of oil ash, vanadium slag deposits in fossil fuel burning apparatus, preventing metal fouling problems and inhibiting corrosion by increasing ash melting temperatures sufiiciently to eliminate the presence of corrosive liquid phases. Whereas the use of silicon additives have provided excellent control of oil ash deposit formation on turbine blades at temperatures below 1300 F., permitting continuous base load type operation with residual grade fuels and operation of power generating turbines for periods of up to 5,000 hours without the necessity for interruption of operation for turbine blade cleaning, the use of silicon despite its effectiveness in preventing fouling of turbine blading and subsequent decrease in output, is not effective in suppressing corrosion at higher operating temperature levels.

As metal temperatures in gas turbines increase and approach 1500 F.1600 F. temperature range, corrosion becomes increasingly important and eventually the dominant problem, since the effect is to pass the critical temperature, at which ash components form corrosive liquid phases, and under these conditions it has been impractical to utilize ash containing or residual fuels within the present state of the art even with the use of fuel additives.

The system of fuel treatment that has been used with varying degrees of success at temperatures up to about 1400 F. and which has permitted operation of gas turbines with ash containing fuels for peaking service for power generation, consists of water washing of the fuel for the virtual elimination of alkali metal salts (sodium and potassium) employing a demulsifier to eliminate the wash water, and adding to the washed fuel a saturated water solution of Epsom salts (MgSO .7H O) mechanically dispersed in the fuel prior to combustion at a dosage sufiicient to yield 3 parts by weight of magnesium per part of vanadium in the fuel. This type of fuel treatment has provided generally adequate corrosion control and produces water washable deposits on turbine blading; however, the use of magnesium contributes substantially to the fouling of turbine blading and results in a continual loss of power output. In practice, it is necessary to limit the amount of magnesium within the range of 3-3.5 parts of magnesium per part of vanadium to achieve a balance of corrosion protection on the one hand and to minimize power loss on the other hand.

The operation of peaking turbines has, therefore, been possible with low quality fuels and the use of magnesium additive provided that the sodium content has been reduced to a level of approximately 1-2 p.p.m. Part of the modified ash tends to spall off when the turbine is shut down and water washing can usually completely remove remaining deposits. Such a shutdown and washing, however, requires about six hours, which means that the practice is suitable only for peaking turbines which can be shut down at rather frequent intervals and is not at all suitable for base load turbines requiring extended periods of uninterrupted operation.

Attempts have been made to extend the periods between shutdowns for blade washing by mechanically dislodging ash deposits at intervals designated by the dropoff in efficiency of operation. One such approach has been to introduce ground walnut shells or the like in a manner to impinge on the turbine blades and dislodge ash deposits, a. step which can be taken without any interruption in turbine operation. While this approach results in a partial restoration of turbine efliciency, the restoration is not complete and, after each mechanical dislodging of ash deposits, the restored efliciency becomes progressively lower, until a point is reached where a shutdown for water washing of the blades becomes imperative. This procedure of mechanical dislodging of ash and infrequent water washing of the blades has been used to extend the operating interval, but suffers from the obvious drawback of progressively lower turbine output and efficiency in addition to the inconvenience of the periodic shutdowns for water washing of the blades.

In designing equipment for higher operating temperatures, nickel base and cobalt base alloys have been resorted to, both to provide high temperature metal strength and to improve corrosion resistance. Such alloys are expensive, and usually significantly increase the cost of fuel burning equipment. Consequently, such use is quite limited in boilers; whereas in gas turbine heat and corrosion resistant alloys must be used for turbine blading materials since metal temperatures may be as much as 400 F.- 500 F. higher than in boilers. Unfortunately, the development of such alloys represents a compromise between high hot strength and resistance to hot corrosion; and while the corrosion problem has been reduced by metallurgical advances, techniques of blade coating and blade cooling, the operation of gas turbines at ever increasing combustion gas temperatures to improve efficiency and to increase engine ratings to some extent has had the effect of nullifying such developments, so the gas turbines operating at inlet temperatures about 1300" F. must, for the most part, burn distillate grade liquid fuels or natural gas.

Even with such high grade fuels, a special problem develops when metal temperatures reach about 1400 F. in the form of sulfidation corrosion which is induced by the presence of sulfur and sodium in the fuel or entering in the combustion air, leading to the formation of Na SO as a reactive component of the ash which in turn can react directly with the nickel and chromium content of alloys used for turbine blades leading to rapid destruction of the metal structure. Instances have been known, for example, where equipment expected to have a useful life of the order of 50,000 hours has been rendered inoperative in 7000 hours or less, due to failure of metal parts through sulfidation corrosion.

Since it is virtually impossible to have a completely sulphur-free oil, the approach to combatting sulfidation corrosion would appear to hinge upon virtual elimination of sodium from the fuel by water Washing, provided the washed fuel is not subjected to subsequent contamination prior to burning. If the water washing is done at the refinery and the fuel is then delivered to the user by ocean transport, special care must be taken to eliminate addition of sodium via sea water contamination with a resulting increase in fuel price due to handling requirements. The fuel, however, is not the only source of introduction of sodium. It has been found that in marine applications or industrial installations in close proximity to the ocean or other bodies of salt water where salt spray may be present in the air, the quantities of air used in burning the fuel can introduce more than enough sodium to cause severe sulfidation problems.

ASTM gas turbine specifications set limits of 5 ppm. of sodium and 2 ppm. of vanadium for GT1, GT2, and GT3 fuel specifications which are intended to be burned without the need for any additive for either corrosion or deposit control. Although these specifications were set by the turbine manufacturers and fuel companies, recent industry experience has shown that fuels containing these contaminant levels are wholly unacceptable, and result in rapid destruction of turbine blades in turbines operating with metal temperatures of about 1400 F. and higher.

Magnesium additives which have heretofore been used do not provide satisfactory corrosion inhibition or deposit modification in gas turbines at such high temperatures and are incapable of preventing sulfidation-type corrosion. This coupled with the scarcity and prohibitive costs of distillate fuels, is seriously deterring the more extensive use of the more eflicient high temperature gas turbines.

There is, for example, a growing interest in using gas turbines for industrial power generation, particularly combined cycle plants, and for marine propulsion, but the problem of economically competing with the steam turbine and diesel engine, both of which can operate on low grade fuels, has heretofore seemed insurmountable.

THE INVENTION It has now been discovered in accordance with the present invention that it is possible to greatly reduce and control the problems of corrosion and ash deposition in the firing of fossil fuel burning equipment by utilizing in the operation of the equipment additive components comprising sources of silicon and magnesium, the proportions being such as to provide a combined SiO and MgO equivalent wherein the SiO :MgO ratio is greater than 2:1, and preferably greater than 3:1. Increasing the SiO :MgO ratio provides progressive improvement in the inhibition of corrosion and ash deposition; and the only real upper limit to this ratio is an economic one based on cost of the additive components.

In referring to a combined Si0 and MgO equivalent it is to be understood that the sources of silicon and magnesium can be widely varied so long as they provide SiO and MgO at the temperatures encountered in the combustion zone and ash deposition zone of fossil fuel burning equipment. Thus the additive components can be organic compounds, inorganic compounds, or mixtures thereof, and such compounds or mixtures thereof can be either soluble or dispersible in water or oil. They can be individually or collectively blended with the bulk fossil fuel prior to burning, introduced to the combustion zone separately from the fuel, or in the case of furnaces and boilers, introduced directly to the ash deposition zone.

By way of illustration, sources of magnesium include materials such as Epsom salt, magnesium acetate and magnesium chloride which are water soluble, magnesium hydroxide, magnesium oxide and magnesium carbonate in the form of finely divided dispersible powders, talc, and certain clays, and natural or synthetic magnesium silicates, which would supply both magnesium and part of the required silicon, and which can be supplied as dry powder dispersible in aqueous or organic liquid media, and magnesium sulfonate, naphthanate, oleate, octoate, and the like, which are oil soluble.

As sources of silica, typical examples include finely divided or colloidal silicas, finely divided inorganic silicates, and organic silicon compounds including in particular silicones, polysilicones, lower alkyl silicates such as tetra-lower-alkyl ortho silicates, mixed ethyl polysilicates, and the like.

The preparation of aqueous solutions and aqueous dispersions can be effected by conventional formulating techniques. Similarly, conventional procedures for preparing organic solvent solutions or suspensions can be employed. When an additive composition is to be used in distillate and other high grade fossil fuel such organic solvent suspensions or solutions can be prepared in various light petroleum fractions such as kerosene, No. 2 distillate oil and the like. On the other hand when the additive composition is to be used in lower grade fuel such as residual oils the use of aromatic type solvent is preferred to facilitate uniform blending with the fuel. Such aromatic solvent can suitably be a relatively high boiling liquid substituted naphthalene or di-substituted benzene compound. Typical aromatic solvents of this type which are commercially available include (1) aromatic solvents which contain methylnaphthalene or naphthalene fractions regardless of origin, that is, whether from coal tar or petroleum sources, (2) methylated naphthalene such as alpha-methyl naphthalene, beta-methylnaphthalene, mixtures of these and derivatives thereof, and (3) chlorinated solvents such as orthodichlorobenzene.

Advantages of the present invention can be achieved by a number of different approaches. A primary approach involves the use of additive components which are combined with fuel by the user or fuel supplier in which the sources of silicon and magnesium can be finely divided powders for mechanical blending with fuel or fluid preparations of either aqueous or organic liquid base in which the magnesium and silicon sources are uniformly blended in the dissolved and/or suspended state. Such additive compositions provide useful articles of commerce, and can readily be formulated to satisfy the special needs of particular combinations of fossil fuel and fuel burning apparatus.

It is to be understood, however, that it is by no means necessary that the silicon and magnesium sources be added simultaneously or concurrently. They may be separately introduced to the fuel or to the combustion zone; and if a bulk fuel is provided which contains either the magnesium or silicon component in an appropriate amount, the invention can be practiced by introducing the missing silicon or magnesium source in amount to provide a SiO :MgO ratio greater than 2:1.

In dealing with corrosion and ash deposition problems in furnaces and boilers the additive components can be introduced directly to the ash deposition zone, as for example by introducing additive components through the soot blowers during the periodic use of such blowers.

It can also be desirable when large amounts of similarly treated fuel are needed for large installations or different smaller installations for the additive components to be incorporated in the fuel by the supplier, in which event the specially treated fuel becomes an improved article of commerce.

The method of utilizing the present invention differs somewhat depending upon the type of fossil fuel burning apparatus involved. In the combustion of fossil fuel in furnaces, boilers and diesels, the additive components should be present in amounts to provide at least 0.05 parts by weight of combined Si0 and MgO equivalent to each part by weight of ash in said fuel. This proportion can be increased to 0.1 parts by weight, and higher if desired. Any such increase in the amount of additive components will further improve the control of corrosion and ash deposition; and from a practical standpoint the upper limit to the amount of additive components is an economic one, with a decision being based on a number of variables including, in addition to the cost of additive, factors such as fuel costs and relative efiiciency of the apparatus with difierent degrees of control of corrosion and ash deposition.

When additive is introduced to the combustion zone independently of the fuel, the dosage should generally correspond to the dosage which would be used if combined directly with the fuel. On the other hand, in furnaces and boilers where additive may be introduced directly to the ash deposition zone, as through the soot blowers with which many furnaces and boilers are equipped, the amount of additive required may be only 10 to 30% the amount required when added to the fuel or introduced directly to the combustion chamber. Such introduction of additive to the ash deposition zone do as not prevent ash deposition, as does introduction to the fuel and to the combustion chamber, but rather provides a means for periodically removing ash deposits already formed, thereby restoring efficiency in operation of the equipment.

The operation of gas turbines with fossil fuel presents a somewhat different situation due to the substantially higher metal temperatures of the turbine blading. In the combustion of fossil fuel in gas turbines, where either or both vanadium and alkali metal will be present in the combustion products, the additive components should be present in amounts to provide at least 2 parts, and preferably about 3 parts, by weight of magnesium to each part of weight of vanadium in said fuel, with the SiO :MgO ratio of said components being such as to provide at least 2 parts by weight of silicon to each part by weight of alkali metal in said fuel and in the air combining therewith on combustion. For inland installation it is unlikely that alkali metal will be introduced in the combustion air. On the other hand, with gas turbines used for marine propulsion or in land-based installations close to bodies of salt water the amount of alkali metal introduced by salt spray in the combustion air can contribute significantly to the amount of alkali metal present in the combustion products.

As has been earlier pointed out, the traces of sulfur which are almost always present in fossil fuels and alkali metals lead to the destructive sulfidation corrosion when gas turbines are operated at the higher temperatures such that the blading metal temperatures are in the range of 1400l600 F. and higher. For this type of operation it is desirable to substantially increase the SiO :MgO ratio so as to provide a SizNa ratio of the order of 6:1 or higher. This appears to prevent Na SO from collecting in the fused state on the turbine blading, and in so doing to greatly minimize or prevent the destructive action of NagSO on alloy components such as nickel and chromium in the turbine blading. In fact, the indications are that when using additives of the present invention with dosage and Si :MgO ratio geared to the amount of alkali metal in the combustion products, the amount of alkali metal in the combustion products can be substantially increased without detrimental effect. This can involve substantial economic significance since the necessity for virtual elimination of the alkali metal content of fossil fuels adds considerably to fuel costs.

Not only does the use of magnesium-silicon additives in accordance with the present invention overcome the serious problem of sulfidation corrosion in high temperature gas turbine operation when using high grade fuel recommended for such operation, but the indications are that the improved additives will also make practical the use of substantially lower grade fuel in high temperature gas turbine operation. Such a possibility is being actively pursued, as the use of certain crude oils and other lower grade fuels in high temperature gas turbine operation could lead to considerable expansion in the use of the gas turbine for utility power generation and marine propulsion.

emulsifiers, or de-emulsifiers can be employed where indicated by the nature of the fuel being treated. So long as additive compositions or treated fuels contain sources of magnesium and silicon in the proportions, and in the amounts herein disclosed, such additive compositions and treated fuels are considered as falling Within the present invention, regardless of whether or not supplementary additive components may be present as above mentioned.

The following examples are presented to show some of the advantages which can be realized in utilizing additive components and methods of the present invention, but it is to be understood that these examples are given by way of illustration and not of limitation.

EXAMPLE I A series of corrosion and ash deposition tests were conducted on metal specimens simulating gas turbine blades using special equipment which is referred to as a high pressure corrosion test passage. This equipment, which closely approximates conditions in real gas turbines, has been described and illustrated in Paper No. 70-WA/ CD-2, an ASME publication presented at the Annual Meeting, in New York, N.Y., Nov. 30 to Dec. 3, 1970, of The American Society of Mechanical Engineers entitled Laboratory Procedures for Evaluating High- Temperature Corrosion Resistance of Gas Turbine Alloys.

In the tests, the specimens employed were formed of Udimet 500, one of the nickel based superalloys described in said publication.

The fuel employed in the tests was No. 2 fuel oil containing ppm. of vanadium and no sodium, and the tests were run for 10 hours at a pressure of 3 atmospheres and with the specimen temperature at 1500 F.

In separate tests, additives were incorporated in the oil providing sources of magnesium alone, silicon alone, and three different silicon/magnesium mixtures.

The test fuel providing a source of magnesium alone was prepared adding to the oil a dispersion of Mg(OH) in paraflinic oil, said dispersion containing 31% by weight of MgO.

The test fuel providing a source of silicon alone was prepared by adding to the oil a solution of silicone polymer in high boiling aromatic solvent (a methylnaphthalene fraction having a boiling range of 450 to 700 F.), said solution containing 33% by weight of SiO;.

The test fuels providing sources of both magnesium and silicon were prepared using high boiling aromatic solvent solutions of organic magnesium and silicon sources. More particularly, magnesium sulfonate containing 12% by weight MgO and silicone polymer containing by weight SiO: were dissolved in a methylnaphthalene fraction having a boiling range of 450 to 700 F. in amounts to provide 14 to 20% by weight of combined MgO and Si0 equivalent, and in proportions to provide the 'SiO /MgO ratios shown in the following table.

At the end of the 10 hour tests, the specimens were examined for corrosion and for the nature of ash deposition, and the results are presented in the following table:

Dosage of Weight ratio P.p.n1. in fuel Test Additive SiOz/MgO Mg/V Mg Si Corrosion Deposits a Mg 3/1 150 Some spots corroded Heavy accumulation very hard and brittle deposit. Evidence of melting.

184 Severely corroded Slight accumulation of soft deposit. 0 Si/Mg l. 5 3/1 150 78 No corrosion Moderate amount of soft and trail deposit. d Si/Mg 1. 5/1 3/1 150 o Similar to 0 but smaller amount. e Si/Mg 3/1 3/1 150 350 ......do Similar to c and d but. still smaller amount.

It will also be understood that additive compositions and treated fuels in accordance with the present invention may contain other additives components having known beneficial effects in particular fuels. By Way of illustrationsmall amounts of a manganese source or other catalyst for The data clearly demonstrate a synergistic effect of the Si/Mg combination additive in inhibiting both corrosion and ash deposits. The soft frail deposits formed when using the Si/ Mg additives are a distinct improvement over the hard brittle deposits when using additive supplying the suppression of $0 as well as combustion improvers, only magnesium. It is the heavy accumulation of deposit,

characteristic of the use of additive containing magnesium without the silicon, that causes the reduction in turbine power output and limits the use of gas turbines for base load type operations. There is special advantage, however, in reducing the quantity of even the soft. frail de- 10 The additive composition used was similar to that described in Example II, i.e., a solution of magnesium sulfonate and silicone polymer in high boiling aromatic solvent containing 14% of combined SiO and MgO equivalent, providing a 'Sio zMgo ratio of 3 :1 in the fuel.

posits by increasing the SiO /MgO ratio in the additive 5 When operating this equipment on the fuel above dcto 2:1 and higher to permit base load type operations. scribed without additive a hard vanadium slag deposit Similar results are obtained in other comparative tests forms in the tube which is very difficult to remove. using as alloy specimens other nickel based superalloys, When additive is incorporated in the fuel at a v./v. Inco 713C, Inco 738, and Udimet 710, and a cobalt based dosage of 1/500, providing 447 p.p.m. of combined superalloy X-45 disclosed in said publication. SiO +Mg0 equivalent i h fuel, th ratio of SiO +M O EXAMPLE H to ash of 0.475/1, the ash deposit becomes a non-bonding but accumulating soft powder. In 18 days the buildup In order to evaluate the effect of increasing proportions f this ft powder was found to produce an increase in of silicon in the magnesium-silicon fuel oil additives on d ft equivalent to 3 inches of water the reduction of corrosion of turbine blade alloys due to when the additive dosage was mdlced to 1/1500 fuel combustion products, several comparative tests were viding 148 ppm. of SiO2.Mg0 equivalent in the oil with m i i hlgh Pressure, common test r the ratio of SiO +MgO to ash being 0.157/1 the ash descnPed m QP I bummg 2 fuel E to whlch accumulated as a moderate amount of friable porous vaqadmm and sodlum had 196811 added pmvlde 5 P- 20 deposit. to 67 days the buildup of this deposit only insodlmfn and 2 Vanadmm- The tests were of 50 creased the draft by the equivalent of 4 inches of water. duration at a pressure of S atmospheres and a testspeci- It will be apparent that the additive pwvides a temperature of Teits run usmg as tinct improvement in the character of the ash and the ease turbu}e,b1ade Udlmet a mckel baed alloy of removal, and that with the particular combination of contam-mg substanual 2 of f; chrommmzand fuel and equipment the lower additive dosage of 1/ 1500 other and Udlmet another mckel v./v. is distinctly superior in providing a much slower i 3110}, qontammg lesser almounts of cobalt and buildup of ash deposit. It can be noted in this connection a Slgmficant f l' of Iron 9 components increase in draft due to ash deposits provides an indicaconimls fl nm wlthoilt any addltlle and tests were tion of quality of the oif gases being discharged to the q g giq to W 2. 1 ratio 85 Mgzv atmosphere. The greater the increase in the draft, the ii a a Ea P 1 f g g greater is the tendency for unburned fuel and objec- 51 1 ig gz z s 'gg gi g i tionable combustion products to be discharged into the nesium sulfonate contahin eight M b i atmosphere; and with the equipment described it had been g a y w g generally necessary to shut down and clean slag deposits an orgamcfilhcop source ilhcone p p PP from the tubes by turbining when the draft increases by welght S102 were dlssolved m hlgh bolhng reached the equivalent of 3-4 inches of water Solvent a P E F fraction havmg. a Various changes and modifications in the additive coml a i il gb lfy v%iglZ? hf 3m hin i 2 g positions, treated fuels, and methods for utilizing the equivalent. 2 40 same as disclosed in the present application may be ap- Pertinent data concerning the dosage weight ratios, and paint those Signed g and to the extent that the observed corrosion (weight loss) expressed in mg./ sue c ange? canons are embraced the are presented in the following table Also included appended claims it is to be understood that they constitute are figures for percent of untreated ash corrosion, and P of fi pr?sent these figures are plotted against SizNa ratio on a graph What 13 fi P 1s: 0 hi h i presented as FIG, 1, 1. An additive composition for mhibitmg corrosion Dosage weight ratio of- Blade corrosion (mg./cm.

U-500, U-710, Additive S10zfMg0 Mg/V MgO/V SiOz/Na Si/Na percent; percent on 11/1 3': 42 ii 3 si g 1.5 1 3 1 5/1 .2 43. iii iii iii 13% iifi 2%? iii the 21.3

1 Percent of corrosion based on 100% for the control test with no additive.

While these results indicate that corrosion varies conand ash deposition in fossil fuel burning equipment, said siderably with changes in alloy composition, what is significaut is the general similarity of the two curves, and that on the average a 2:1 ratio of silicon to sodium provides about 50% reduction in corrosion (for Udimet 710 the reduction is slightly less than 50% and for Udimet 500 the reduction is substantially more than 50%). The very low corrosion and the slope of the curves in the 5:1 to 6:1 Si:Na range suggest that slight further increase in the SizNa ratio could be beneficial with some alloys.

EXAMPLE III composition consisting essentially of compounds of silicon and magnesium which form SiO and MgO at fuel combustion temperature, the quantities of said compounds being such as to provide a combined SK); and MgO equivalent wherein the SiO :MgO ratio is greater than 2:1.

2. An additive composition for inhibiting corrosion and ash deposition as defin in claim 1, wherein the said compounds of silicon and magnesium are selected from the group consisting of organic compounds, inorganic compounds and mixtures thereof, which compounds or mixtures thereof may be either soluble or dispersible in water or oil.

3. An additive composition as defined in claim 1, wherein the SiO :MgO ratio is preferably greater than 3:1.

4. A fossile fuel composition for use in fuel burning equipment comprising a major amount of ash containing fuel having blended therewith additive components consisting essentially of compounds of silicon and magnesium which form SiO and MgO at fuel combustion temperature, the proportions of said compounds being such as to provide a combined SiO and MgO equivalent wherein the SiO :MgO ratio is greater than 2:1, the quantity of said additive components being such as to provide at least 0.05 parts by weight of combined SiO and MgO equivalent to each part by weight of ash in said fuel.

5. A fossil fuel composition for use in gas turbines comprising a major amount of fuel, characterized as containing at least one of the contaminants, vanadium and alkali metal, having blended therewith additive components consisting essentially of compounds of silicon and magnesium which form Si and MgO at fuel combustion temperature, the proportions of said compounds being such as to provide a combined SiO and MgO equivalent wherein the SiO :MgO ratio is greater than 2:1, the quantity of said additive components being such as to provide a minimum of 2 parts by weight of magnesium to each part by weight of vanadium in said fuel, with the SiO :MgO ratio of said components being such as to provide at least 2 parts by weight of silicon to each part by weight of alkali metal in said fuel.

6. A fossil fuel composition for use in gas turbines 12 of said compounds being such as to provide a combined Si02 and MgO equivalent wherein the siO zMgO ratio is greater than 2:1, the quantity of said additive components being such as to provide at least two parts by weight of silicon to each part by weight of alkali metal in the combustion products to the turbine.

7. A fossile fuel composition as defined in claim 6 wherein the quantity of said additive components preferably provides at least 6 parts by weight of silicon to each part by weight of alkali metal in the combustion products to the turbine.

References Cited UNITED STATES PATENTS 2,843,200 7/ 1958 Rocchini 44--68 X 3,003,857 10/1961 Carls 44DIG. 003 3,316,070 4/ 1967 Scott 4451 FOREIGN PATENTS 744,141 2/ 1956. Great Britain 44--DIG. 003 761,360 11/1956 Great Britain 44DIG. 003 761,378 11/ 1956 Great Britain 44DIG. 003 764,752 1/ 1957 Great Britain 44DIG. 003

operating in a marine or similar environment subject PATRICK GARVIN, Primary Examiner to ingestion of sea salts in the combustion air comprising a major amount of distillate fuel having blended therewith additive components consisting essentially of compounds of silicon and magnesium which form SiO and MgO at fuel combustion temperature, the proportions A. H. METZ, Assistant Examiner US. Cl. X.-R.

44-5l, 68, DIG. 003

Disclaimer 3,817,722.James F. Scott. Briarcliff Manor, N.Y. COMPOSITIONS FOR INHIBITING CORROSION AND ASH DEPOSITION IN FOS- SIL FUEL BURNING EQUIPMENT. Patent dated June 18, 1974. Disclaimer filed Mar. 17, 1975, by the assignee, The Pemlz'n 00mpany, l'ne. Hereby enters this disclaimer to claims 1, 2, 3 and 4 of said patent.

[Oyficial Gazette July 22, 1 975.] 

